Electronic industries

Clusters are intennediates bridging the properties of the atoms and the bulk. They can be viewed as novel molecules, but different from ordinary molecules, in that they can have various compositions and multiple shapes. Bare clusters are usually quite reactive and unstable against aggregation and have to be studied in vacuum or inert matrices. Interest in clusters comes from a wide range of fields. Clusters are used as models to investigate surface and bulk properties [2]. Since most catalysts are dispersed metal particles [3], isolated clusters provide ideal systems to understand catalytic mechanisms. The versatility of their shapes and compositions make clusters novel molecular systems to extend our concept of chemical bonding, stmcture and dynamics. Stable clusters or passivated clusters can be used as building blocks for new materials or new electronic devices [4] and this aspect has now led to a whole new direction of research into nanoparticles and quantum dots (see chapter C2.17). As the size of electronic devices approaches ever smaller dimensions [5], the new chemical and physical properties of clusters will be relevant to the future of the electronics industry. 

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Cyanoacrylate adhesives (Super-Glues) are materials which rapidly polymerize at room temperature. The standard monomer for a cyanoacrylate adhesive is ethyl 2-cyanoacrylate [7085-85-0], which readily undergoes anionic polymerization. Very rapid cure of these materials has made them widely used in the electronics industry for speaker magnet mounting, as weU as for wire tacking and other apphcations requiring rapid assembly. Anionic polymerization of a cyanoacrylate adhesive is normally initiated by water. Therefore, atmospheric humidity or the surface moisture content must be at a certain level for polymerization to take place. These adhesives are not cross-linked as are the surface-activated acryhcs. Rather, the cyanoacrylate material is a thermoplastic, and thus, the adhesives typically have poor temperature resistance. 

ASTM has pubhshed a few selected standards for materials used in the electronics industry, such as gold wire for semiconductor lead bonding, but it does not provide a comprehensive set of standards (see Electrecal connectors). 

A small but significant use for aqueous HF is in the electronics industry (see Electronic materials). Aqueous HE (typically 49%) of extremely high purity is used as an etchant for sihcon wafers (see Ultrapurematerials). 

Miscellaneous Applications. Ben2otrifluoride derivatives have been incorporated into polymers for different appHcations. 2,4-Dichloroben2otrifluoride or 2,3,5,6-tetrafluoroben2otrifluoride [651-80-9] have been condensed with bisphenol A [80-05-7] to give ben2otrifluoride aryl ether semipermeable gas membranes (336,337). 3,5-Diaminoben2otrifluoride [368-53-6] and aromatic dianhydrides form polyimide resins for high temperature composites (qv) and adhesives (qv), as well as in the electronics industry (338,339). 

Gels. Fluorosihcone fluids with vinyl functionahty can be cured using the platinum catalyst addition reactions. The cure can be controlled such that a gel or a soft, clear, jelly-like form is achieved. Gels with low (12% after 7 d) swell in gasoline fuel are useflil (9) to protect electronics or circuitry from dust, dirt, fuels, and solvents in both hot (up to 150°C) and cold (down to —65° C) environments. Apphcations include automotive, aerospace, and electronic industries, where harsh fuel—solvent conditions exist while performance requirements remain high. 

Antistatic protection is an important consideration within the electronic industry and various antistatic agents are used commercially to aUeviate this problem in cushion packaging materials. 

Ultrahigh Purity Gallium. Many appHcations, particularly those in the electronics industry (see Electronic materials), require high (>99.99999% = 7.N ) purity metallic galHum. This is achieved by a combination of several operations such as filtration, electrochemical refining, heating under vacuum, and/or fractional crystalli2ation (see Ultrapure materials) (14). 

Electrical. Glasses are used in the electrical and electronic industries as insulators, lamp envelopes, cathode ray tubes, and encapsulators and protectors for microcircuit components, etc. Besides their abiUty to seal to metals and other glasses and to hold a vacuum and resist chemical attack, their electrical properties can be tailored to meet a wide range of needs. Generally, a glass has a high electrical resistivity, a high resistance to dielectric breakdown, and a low power factor and dielectric loss. 

Small, complex-shaped glass articles such as thread guides for the textile industry and television gun mounts for the electronics industry are made by the multiform process. The dry-milled powder is mixed with an inorganic binder and a fluid vehicle, and then atomi2ed by a spray dryer into small, dried agglomerates of glass powder and binder with good flow characteristics. They are subsequently pressed to the desired shape and fired. 

In the electronics industry, gold is used as fine wires or thin film coatings and frequendy in the form of alloys to economize on gold consumption and to impart properties such as hardness. Gold has properties that satisfy specific requirements not achievable with less expensive metals (see Electrical connectors Electronics coatings Thin films). 

In the electronics industry. Pis find wide appHcations as a dielectric material for semiconductors due to thermal stabiHty (up to 400°C) and low dielectric constant. Pis are being considered for use in bearings, gears, seals, and prosthetic human joints. The intended part can be machined or molded from the PI, or a film of PI can be appHed to a metallic part. Because of their superior adhesion, dielectric integrity, processing compatibUity, and lack of biological system impact. Pis have been used in many biological appHcations with particular success as body implants. 

PPQs possess a stepladder stmcture that combines good thermal stabiUty, electrical insulation, and chemical resistance with good processing characteristics (81). These properties allow unique appHcations in the aerospace and electronics industries (82,83). PPQ can be made conductive by the use of an electrochemical oxidation method (84). The conductivities of these films vary from 10 to 10 S/cm depending on the dopant anions, thus finding appHcations in electronics industry. Similarly, some thermally stable PQs with low dielectric constants have been produced for microelectronic appHcations (85). Thin films of PQs have been used in nonlinear optical appHcations (86,87). 

Electronic. The largest use of helium-group gases in the electronics industry is for the manufacture of semiconducting devices. The starting... 

Silane, pure or doped, is used to prepare semiconducting siUcon by thermal decomposition at >600° C. Gaseous dopants such as germane, arsine, or diborane maybe added to the silane at very low concentrations in the epitaxial growing of semiconducting siUcon for the electronics industry. Higher silanes, eg, Si H and Si Hg, are known but are less stable than SiH. These are analogues of lower saturated hydrocarbons. 

Arsine. Arsine is a highly toxic colodess gas, made in small amounts as a dopant for siUcon in the electronics industry by the reaction... 

Although the principal appHcation of reverse osmosis membranes is still desalination of brackish water or seawater to provide drinking water, a significant market is production of ultrapure water. Such water is used in steam boilers or in the electronics industry, where huge amounts of extremely pure water with a total salt concentration significantly below 1 ppm are required to wash siUcon wafers. 

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